A variety of effector-specific protein kinases have been identified in brain tissue and, most recently, a cyclic nucleotide-independent protein kinase has been the subject of much interest. This particular protein kinase is stimulated by phospholipids in the presence of calcium. This phospholipid-sensitive kinase can apparently be distinguished from a calmodulin (CaM)-activated protein kinase on the basis of substrate specificity. Howver, it has not been demonstrated with certainty that the phospholipid- and CaM-activated protein kinase are distinct enzymes, nor has a phospholipid-specific protein kinase been demonstrated. We have demonstrated that the activation of protein kinase by phospholipids can be mimicked by sodium dodecylsulfate (SDS), as well as the hydrophobic probe 8-anilino-1-napthalene-sulfonate (ANS), indicating that the phospholipid effect on protein kinase represents a more general stimulation of enzyme activity than previously indicated.